The invention relates to reducing hair growth in mammals, particularly for cosmetic purposes.
A main function of mammalian hair is to provide environmental protection. However, that function has largely been lost in humans, in whom hair is kept or removed from various parts of the body essentially for cosmetic reasons. For example, it is generally preferred to have hair on the scalp but not on the face.
Various procedures have been employed to remove unwanted hair, including shaving, electrolysis, depilatory creams or lotions, waxing, plucking, and therapeutic antiandrogens. These conventional procedures generally have drawbacks associated with them. Shaving, for instance, can cause nicks and cuts, and can leave a perception of an increase in the rate of hair regrowth. Shaving also can leave an undesirable stubble. Electrolysis, on the other hand, can keep a treated area free of hair for prolonged periods of time, but can be expensive, painful, and sometimes leaves scarring. Depilatory creams, though very effective, typically are not recommended for frequent use due to their high irritancy potential. Waxing and plucking can cause pain, discomfort, and poor removal of short hair. Finally, antiandrogens--which have been used to treat female hirsutism--can have unwanted side effects.
It has previously been disclosed that the rate and character of hair growth can be altered by applying to the skin inhibitors of certain enzymes. These inhibitors include inhibitors of 5-alpha reductase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, gamma-glutamyl transpeptidase, and transglutaminase. See, for example, Breuer et al., U.S. Pat. No. 4,885,289; Shander, U.S. Pat. No. 4,720,489; Ahluwalia, U.S. Pat. No. 5,095,007; Ahluwalia et al., U.S. Pat. No. 5,096,911; and Shander et al., U.S. Pat. No. 5,132,293.
Ceramide is a naturally occurring sphingolipid metabolite present in skin and other tissues both intra- and extra-cellularly. Biosynthesis of ceramide in cells generally starts by the condensation of the amino acid serine and palmitoyl-CoA resulting in the formation of 3-ketodihydrosphingosine, which is subsequently reduced to dihydrosphingosine. The amide linkage of fatty acyl groups to dihydrosphingosine forms dihydroceramide. The dihydroceramide is converted to ceramide by the introduction of a trans-4,5-double bond. Once formed, ceramide acts as a precursor for the synthesis of other complex sphingolipids such as galactosylceramide, glucosylceramide, and acyl ceramide. Most glycosphingolipids are synthesized from ceramide via glucosylceramide, the formation of which is catalyzed by glucosylceramide synthase.
Ceramide is also formed in cells by pathways of complex glycosphingolipid catabolism. For example, the breakdown of sphingomyelin through the action of sphingomyelinases results in the formation of ceramide. Another set of enzymes that may regulate cellular ceramide levels are ceramidases, which break down ceramide to sphingosine.